fn parse_request(mut parts: std::str::SplitWhitespace<'_>) -> RequestParserResult<'_> {

        let songid = parts.next().ok_or(RequestParserError::UnexpectedEOF)?;

        let songid = songid

            .parse()

            .map_err(|_| RequestParserError::SyntaxError(0, songid.to_string()))?;

        let tag_name = parts.next().ok_or(RequestParserError::UnexpectedEOF)?;

        let tag_name = tag_name

            .parse()

            .map_err(|_| RequestParserError::SyntaxError(0, tag_name.to_string()))?;

        let tag_value = parts.next().ok_or(RequestParserError::UnexpectedEOF)?;

        let tag_value = tag_value

            .parse()

            .map_err(|_| RequestParserError::SyntaxError(0, tag_value.to_string()))?;

        debug_assert!(parts.next().is_none());

        Ok((Request::AddTagId(songid, tag_name, tag_value), ""))

    }

    fn parse_response(

        parts: ResponseAttributes<'_>,

    ) -> Result<Self::Response, ResponseParserError> {

        debug_assert!(parts.is_empty());

        Ok(())

    }